(1) Field of the Invention
The present invention relates to a packet forwarding apparatus and, more particularly, to a packet forwarding apparatus capable of connecting between a mobile network and a plurality of ISP networks and selectively connecting a mobile terminal to an ISP network with which the mobile terminal has a service contract.
(2) Description of Related Art
In recent years, broadband environments for access from end users to the Internet have been developed rapidly with high-speed access line technology such as Asynchronous Digital Subscriber Line (ADSL), Fiber to the Home (FTTH), and CATV. Internet usage is diversified and Internet access from terminals connected to a mobile communication network increases rapidly.
As a communication protocol for IP communication on a mobile communication network, Mobile IPv6 specifications are standardized in RFC 3775 of the Internet Engineering Task Force (IETF). The Mobile IPv6 basically inherits IPv4-adaptive Mobile IP functions specified in RFC 3220. A Mobile IPv6 network comprises mobile nodes (MNs), home agents (HAs), and correspondent nodes (CNs), wherein each MN is assigned its home address HoA which remains unchanged while the MN roams.
When a mobile node MN leaves its home link having the same prefix as HoA and moves to another link (a foreign link), the MN obtains a Care of Address (CoA) to be used there. The MN receives a Router. Advertisement (RA) message which is periodically transmitted by a router located in the foreign link and recognizes that it has moved to another link by detecting that the source address of the received message has a prefix different from its HoA or its current CoA.
When getting a new CoA in the foreign link, the MN transmits a location registration request message BU (Binding Update) including the HoA and the new CoA to its home agent HA. Upon receiving the BU message from the MN, the home agent HA stores the HoA and CoA indicated in the received message into a Binding Cache management table as binding information and multicasts a control message to adjacent routers so that the HA can capture packets destined to the HoA of the MN. In consequence, a packet transmitted from a correspondent node CN, addressed to the HoA of the MN, are captured by the HA. Upon receiving the packet addressed to the HoA of the MN, the HA adds an encapsulation header including the CoA of the MN as the destination address to the received packet and forwards the packet to the foreign link to which the MN is visiting.
As communication protocols that apply to the communication between MN and HA in Mobile IP, the following are known: e.g., Internet Security Association and Key Management Protocol (ISAKMP) defined in RFC 2408, The Internet Key Exchange (IKE) defined in RFC 2409, and Extended Authentication within ISAKMP/Oakley (Xauth) which is under consideration in draft-ietf-ipsec-isakmp-xauth-06.
In the case of IPv4, CoA can be obtained from a DHCP (Dynamic Host Configuration Protocol) server. In the case of IPv6, CoA can be generated automatically by combining a prefix value of the source address (router address) of an RA message and a part of the MAC address of the MN.
As regards HoA assignment, for example, Japanese Unexamined Patent Publication No. 2005-364271 proposes a method for use in a mobile network system where a whole local network including mobile nodes and a mobile router is movable. In this prior art, the mobile router transmits a request for HoA assignment to a location management server and the location management server notifies the mobile router of an unused address retrieved from an address management table as HoA.
From a viewpoint of how the service is provided, Internet access service is classified into all-in-one provider type access service and selective provider type access service.
In the all-in-one provider type access service, access line service to provide an access line to a user and Internet connection service is offered by the same provider entity. Current mobile communication networks are operated with this type of Internet access. On the other hand, in the selective provider type access service, an access line such as ADSL and FTTH is offered from an access line provider and Internet connection service is offered by a plurality of Internet Service Providers (ISPs) different from the access line provider.
In a stationary communication network, the selective provider type access service is applied in a historical consequence and to meet user preference. As a typical network configuration for realizing the selective provider type access service, a scheme is known in which a connection is set up via a Layer 2 Tunneling Protocol (L2TP) on a user-by-user basis between an LAC (L2TP access concentrator) accommodating access lines provided by an access line provider and an LNS (L2TP Network Server) to which an ISP network managed by an ISP is connected.